arrant

Particularly used in the phrase “arrant knaves”, quoting Hamlet, and “arrant nonsense”.

Some dictionaries consider arrant simply an alternative form of errant, but in usage they have long split.

The word has long been considered archaic, may be confused with errant, and is used primarily in clichés, on which basis some recommend against using it.

Origin

Alteration of errant. Originally meaning wandering (errant), the term came to be an intensifier due to its use as an epithet, e.g. in the phrases "arrant thieves" and "arrant knaves" (i.e., wandering bandits).